Near-eye image projection system and wearable device comprising said near-eye image projection system

ABSTRACT

Near-eye image projection system having a pin-light source generating incident light beams; a SLM generating modulated light beams forming pin-light images at a first plane; illumination optics, in a third plane, delivering the incident light beams from the pin-light source to the SLM; and imaging optics delivering the modulated light beams along a projection axis, in a fourth plane, to an eye-box in a second plane parallel to the first plane. The third and fourth planes being substantially perpendicular to the first plane. The illumination optics defines a first optical path from the first plane to the second plane and a second optical path from the third plane to the fourth plane. The imaging optics defines a third optical path from the second plane to the first plane and a fourth optical path from the first plane to the second plane. A wearable device having the near-eye image projection system is also described.

TECHNICAL DOMAIN

The present invention concerns a near-eye image projection system havingsmall form factor. The present invention further concerns a wearabledevice comprising said near-eye image projection system, such asaugmented/mixed reality or smart glasses. More particularly the presentinvention concerns a near-eye light-field projection system. Thenear-eye light-field projection system can have foveation capability.

RELATED ART

Light-field image projection by means of sequential spatial lightmodulation of structured incident light by a spatial light modulator(SLM) typically requires that the source light from a light source isshaped by several optical elements that are separated by sufficientvolume of a transparent medium in order to achieve the requiredcharacteristics of the structured incident light and, therefore, of theprojected light-field image. Such arrangement results in a bulkierdevice that is not suitable for use in applications where smallform-factor is required, such as in wearable devices, e.g. smartglasses. Shrinking the optics by using higher power optical elements,such as lenses with shorter focal length, freeform optics, etc. stillrequires substantial volume for light propagation, or is penalized bythe lower quality of the illumination light structure and, consequently,of the projected image, and higher compensation requirements due tooptical artifacts such as distortions, aberrations, diffractions, etc.

Document EP3542206A1 discloses a method of light-field projection bysequential spatial light-modulation of structure light. DocumentWO2020157562A1 discloses several methods of combination of light-fieldprojection system with different types of combiners and documentUS20190285897A1 discloses an apparatus using image pupil expansion witha waveguide in combination with a reflective combiner.

SUMMARY

The present disclosure concerns a near-eye image projection system,comprising a pin-light source generating a plurality of incident lightbeams; a SLM configured to modulate said plurality of incident lightbeams and generate a plurality of modulated light beams such as to formpin-light images at a first plane; illumination optics and imagingoptics configured to deliver the incident light beams from the pin-lightsource to the SLM. The imaging optics is further configured to deliversequentially the modulated light beams from the SLM along a projectionaxis to an eye-box in a second plane substantially parallel to the firstplane. The illumination optics is in a third plane and the projectionaxis is in a fourth plane; the third and fourth planes are substantiallyperpendicular to the first plane. The illumination optics defines afirst optical path followed by the incident light beams in a directionfrom the first plane to the second plane, and a second optical pathfollowed by the incident light beams in a direction from the third planeto the fourth plane. The imaging optics defines a third optical pathfollowed by the modulated light beams in a direction from the secondplane to the first plane, and a fourth optical path followed by themodulated light beams in a direction from the first plane o the secondplane. The imaging optics further comprises an optical combiner toproject image light beams from the modulated light beams and to transmitnatural light from the real world towards the eye-box, wherein themodulated light beams comprise foveal modulated light beams formingfoveal pin-light images at the first plane and peripheral modulatedlight beams forming peripheral pin-light images at the first plane, andwherein the optical combiner comprises a foveal combiner configured toreflect the foveal modulated light beams and project foveal image lightbeams towards a foveal eye-box.

The near-eye image projection system disclosed herein has a small formfactor and is well adapted for wearable applications such as foraugmented/mixed reality or smart glasses.

SHORT DESCRIPTION OF THE DRAWINGS

Exemplar embodiments of the invention are disclosed in the descriptionand illustrated by the drawings in which:

FIGS. 1 a to 1 f show a schematic representation of a near-eye imageprojection system comprising a SLM, illumination optics and imagingoptics, according to several embodiments;

FIGS. 2 a to 2 c show the illumination optics, according to severalembodiments;

FIG. 3 illustrates a peripheral image injection optics of the imagingoptics, according to an embodiment;

FIG. 4 a represents an image composed of light-field and peripheralparts as seen from a foveal eye-box;

FIG. 4 b represents an actively foveated image composed of light-fieldand peripheral parts where the light-field part of the image is alignedwith the region of interest such region where the gaze of a viewer ispointing from a foveal eye-box;

FIG. 5 is a schematic representation of mixed reality glasses, accordingto an embodiment; and

FIG. 6 is a top view of the mixed reality glasses of FIG. 5 , worn by auser.

EXAMPLES OF EMBODIMENTS

FIGS. 1 a to 1 f show a schematic representation of a near-eye imageprojection system 200, according to an embodiment. The near-eye imageprojection system 200 comprises a pin-light source 10 generating aplurality of incident light beams 100 a, 100 b. A SLM 20 is configuredto modulate the plurality of incident light beams 100 a, 100 b andgenerate a plurality of modulated light beams 110 a, 110 b and formpin-light images 31, 39 at a first plane 30. The near-eye imageprojection system further comprises illumination optics configured todeliver sequentially the incident light beams 100 a, 100 b from thepin-light source 10 to the SLM 20, along a projection axis 170 a, 170 bto an eye-box 121 a, 121 b in a second plane 124 substantially parallelto the first plane 30.

Referring to FIG. 1 a , the illumination optics is in a third plane 38and the projection axis 170 a, 170 b is in a fourth plane 125. The thirdand fourth planes 38, 125 are substantially perpendicular to the firstplane 30. The illumination optics is configured to define a firstoptical path 171 shown parallel, although not necessarily, to theprojection axis 170 a, 170 b in a first direction, from the first plane30 to the second plane 124. The illumination optics can be furtherconfigured to define a second optical path 172 (shown perpendicular tothe projection axis 170 a, 170 b although not necessarily) from thethird plane 38 to the fourth plane 125.

A possible configuration of the illumination optics is shown in FIG. 2 a, according to an embodiment. The illumination optics comprises apin-light source 10 comprising a plurality of individual pin-lights 10a, each pin-light 10 a being adapted to generate at least an incidentlight beam 100 a, 100 b. In the particular example of FIG. 2 a , thepin-light source 10 comprises an array of pin lights 10 a in a planesubstantially perpendicular to the first plane 30. Other arrangements ofthe pin-light source 10 are however possible.

In one aspect, the illumination optics comprises a collimating opticalelement 50 configured to collimate the incident light beams 100 a, to anarrow beam. The collimating optical element 50 can comprise any one ora plurality of a lens, a mirror, a hologram or any other optical elementperforming the collimation.

In one aspect, the illumination optics further comprises an illuminationdeflecting element 61 configured to redirect the incident pin-lights 100a, 100 b along the first optical path 171. The illumination deflectingelement 61 can comprise any one or a plurality of a prism, a grating, ahologram or any other optical element performing the redirecting.

In one aspect, the illumination optics comprises an illumination pupilexpansion device 36 a configured to expand the incident light beams 100a, 100 b from an entrance of the illumination pupil expansion device 36a to an exit pupil. The illumination pupil expansion device 36 a enablesan increased field of view (FOV) of a projected image.

In one aspect, the illumination pupil expansion device comprises alight-guide or illumination waveguide 36 a including an illuminationin-coupling element 35 a configured to input the incident pin-lights 100a, 100 b. The illumination waveguide 36 a can further include anillumination out-coupling element 37 a configured to output the incidentpin-lights 100 a, 100 b along the second optical path 172.

The collimated incident light beams 100 a, 100 b are injected into theillumination waveguide 36 a by means of interaction with theillumination in-coupling element 35 a. The latter can comprisediffraction gratings, holograms, inclined mirrors or prisms, stack ofsemi-reflective interfaces, or any other suitable optical element. Theincident light beams 100 a, 100 b propagates due to internal reflectionwhile they expand in the plane of the illumination waveguide 36 a bymeans of interaction with 1D or 2D fold gratings or by any other opticalelement expanding the incident light beams 100 a, 100 b. Theillumination out-coupling element 37 a can comprise a diffractiongrating, a hologram, an inclined mirror or prism array, stack ofsemi-reflective interfaces, or any other optical element configured tooutput the incident pin-lights 100 a, 100 b along the second opticalpath 172. The illumination out-coupling element 37 a can be configuredsuch that the incident light beams 100 a, 100 b exit the illuminationwaveguide 36 a multiplicated with homogeneously distributed intensityand collimated in the orientation given by the tilt angle of theinjected incident light beams 100 a, 100 b, the orientation being thesecond optical path 172.

The expanded collimated beams sequentially illuminate the reflective ortransmissive SLM 20. In the case of transmissive SLM, the incident lightcomponents become modulated and propagate to projection optics.

Again referring to FIG. 1 a , the imaging optics is further configuredto define a third optical path 173 (shown parallel to the projectionaxis 170 a, 170 b in the first direction although not necessarily) fromthe second plane 124 to the first plane 30. The imaging optics isfurther configured to define a fourth optical path 174 (shown parallelto the projection axis 170 a, 170 b although not necessarily) from thefirst plane to the second plane 124.

In an embodiment, the imaging optics comprises an illumination andprojection optical element 70. The latter can comprise a prism 70including a first and second beam shaping outer surfaces 52, 53. In thecase of a reflective SLM 20, such as shown in FIG. 1 a , the incidentlight beams 100 a, 100 b exiting the illumination waveguide 36 a by theillumination out-coupling element 37 a along the second optical path172, pass through the first and second beam shaping outer surfaces 52,53 of the prism 70 before it reaches the SLM 20. The first and secondbeam shaping outer surfaces 52, 53 can be configured to concentrate thecollimated incident light beams 100 a, 100 b on the SLM 20.

In one aspect, the prism 70 can include a beam splitter 140 configuredto be traversed by the incident light beams 100 a, 100 b along thesecond optical path 172 before the incident pin-lights 100 a, 100 breach the SLM 20.

The (reflective) SLM 20 modulates the incident light beams 100 a or 100b and reflects the modulated light beams 110 a, 110 b (image components)along the second optical path 172 back to the prism 70 through thesecond beam shaping surface 53. The SLM 20 is further configured toreflect the modulated light beams 110 a, 110 b with in-planepolarization (s-polarization) or higher-than-total internal reflectionangle (in case the SLM 20 comprises a digital micromirror device), whichis obtained during the modulation at the SLM 20.

The beam splitter 140 can be further configured to reflect the modulatedlight beams 110 a, 110 b generated by the SLM 20 along the third opticalpath 173. The prism 70 further includes a third and fourth beam shapingouter surfaces 54, 58. The modulated light beams 110 a, 110 b reflectedby the beam splitter 140 is reflected by the third beam shaping outersurface 54 along the fourth optical path 174.

The third beam shaping outer surface 54 can be configured such that thepolarization of the modulated light beams 110 a, 110 b is reversedrelative to the in-plane polarization provided by the SLM 20.

In one aspect, the third beam shaping outer surface 54 can comprise aquarter-wave plate 56 configured such that the modulated light beams 110a, 110 b along the third optical path 173 becomes p-polarized.

The modulated light beams 110 a, 110 b reflected by the third beamshaping outer surface 54 passes through the fourth beam shaping outersurfaces 58. The fourth beam shaping outer surface 58 can be configuredto collimate the SLM pixel beams that compose the modulated light beams110 a, 110 b.

In an embodiment, the imaging optics comprises an optical combiner 40configured to receive the modulated light beams 110 a, 110 b and projectimage light beams 112 a, 112 b along the projection axis 170 a, 170 b tothe eye-box 121 a, 121 b. The optical combiner 40 is further configuredto transmit natural light from the real world 190 towards the eye-box121 a, 121 b.

The near-eye image projection system 200 is destined to be worn by aviewer for virtual and mixed reality applications. The image projectionsystem can be configured such that, when it is worn by the viewer, theeye-box 121 a, 121 b and an exit pupil (or view point) 120 is within theviewer's eye 90. The image light beams 112 a, 112 b are projectedtowards a pupil 130 of the viewer's eye 90, such that the image lightbeams 112 a, 112 b are projected on the retina 92.

The modulated light beams can comprise foveal modulated light beams 110a forming foveal pin-light images 31 at the first plane 30 andperipheral modulated light beams 110 b forming peripheral pin-lightimages 39 at the first plane 30.

In one aspect, the imaging optics further comprises a Fourier filter 34in the first plane 30. The Fourier filter 34 can comprise imagingdeflecting elements 60 a (see FIG. 3 ) reflecting the foveal modulatedlight beams 110 a to a foveal combiner 41 comprised in the opticalcombiner 40, such that the foveal combiner 41 reflects the fovealmodulated light beams 110 a and projects foveal image light beams 112 atowards a foveal eye-box 121 a. The foveal combiner 41 can comprise atransparent or at least partially transparent reflecting surface. Thereflecting surface can be concave and/or ellipsoid shaped or have anyshape adapted to project foveal image light beams 112 a towards a fovealeye-box 121 a.

In particular, FIG. 1 a shows the pin-light source 10 generating asingle incident foveal light beam 100 a and the projection of a singlefoveal modulated light beam 110 a and foveal image light beam 112 atowards a foveal eye-box 121 a. The single incident foveal light beam100 a is generated by a single pin-light (active pin-light) 10 a of thepin-light source 10. The foveal image light beams 112 a forms an imageat a viewpoint in 120 in the foveal eye-box 121 a.

FIG. 1 b shows the near-eye image projection system 200, wherein asingle incident foveal light beam 100 a is generated by another singlepin-light 10 a of the pin-light source 10. The foveal image light beam112 a forms an image at another viewpoint 120 in the foveal eye-box 121a.

A plurality of pin-lights 10 a of the pin-light source 10 can generate aplurality of incident foveal light beams 100 a and the illuminationoptics and imaging optics project a plurality of foveal modulated lightbeams 110 a and foveal image light beams 112 a towards a foveal eye-box121 a.

The imaging optics can further comprise an imaging mirror 32 configuredto reflect the foveal modulated light beams 110 a reflected by theimaging deflecting elements 60 a to the foveal combiner 41. The imagingmirror 32 can be placed in the vicinity of the SLM 20 such the fovealmodulated light beams 110 a are reflected by the imaging deflectingelements 60 a towards the SLM 20 and reflected back by the imagingmirror 32 towards the foveal combiner 41. The imaging deflectingelements 60 a can comprise inclined mirrors or prisms. The imagingmirror 32 produces foveal modulator images 114 a in a modulator imageplane 115 between the imaging mirror 32 and the foveal combiner 41.Since each of the imaging deflecting elements 60 a can be oriented atdifferent angles (for example, the mirrors or prisms can be inclined atdifferent angles), the foveal modulator images 114 a can create an arraywherein at least some of the foveal modulator images 114 a are spatiallydisplaced in the modulator image plane 115 relative to other fovealmodulator images 114 a. In this case the foveal combiner 41 would causethat the image array is seen by a viewer from the eye box 121 a.

In an embodiment, the imaging mirror 32 can be movable such as todeflect the foveal modulated light beams 110 a reflected by the imagingmirror 32 from the projection axis 170 a, 170 b.

FIG. 1 c illustrates the near-eye image projection system 200, whereintwo foveal modulated light beams 110 a, from two incident foveal lightbeams 100 a generated by the pin-light source 10, are projected along aprojection axis 170 a which is inclined with respect to a central(neutral) projection axis 170 b. The inclination of the projection axis170 a relative to the central projection axis 170 b is a function of themovement (rotation) of the imaging mirror 32.

In one aspect, the near-eye image projection system 200 can comprise aneye-tracking and steering device (not shown) providing eye-trackinginformation. The imaging mirror 32 can then be moved (rotated) inaccordance with eye-tracking information.

In one aspect, the Fourier filter 34 is further configured to let theperipheral modulated light beams 110 b pass through the Fourier filter34 and reach an image injection optics 150 configured to expand theperipheral modulated light beams 110 b from a first angle α to a secondangle β larger than the first angle α.

The Fourier filter 34 can thus be configured to split the optical pathof the foveal modulated light beams 110 a and the peripheral modulatedlight beams 110 b.

FIG. 3 illustrates the peripheral image injection optics 150, accordingto an embodiment. In the configuration of FIG. 3 , the image injectionoptics 150 includes a beam shaping transmissive surface 151 where theperipheral modulated light beams 110 b are inputted. In FIG. 3 , oneperipheral modulated light beam 110 b is shown. The following discussionconsiders one peripheral modulated light beam 110 b but also applies toa plurality of peripheral modulated light beams 110 b. The imageinjection optics 150 further includes a reflective surfaces 152, 153(mirrors 152 and 153) and a beam shaping reflective surface 154.

The inputted peripheral modulated light beam 110 b enters the peripheralimage injection optics 150 with the first angle α through an opening 341in the Fourier filter 34. The opening 341 coincides with the peripheralpin-light image 39 of the peripheral modulated light beam 110 b.

The peripheral modulated light beam 110 b is inputted in the peripheralimage injection optics 150 with a beam angle α through the opening 341.The peripheral modulated light beam 110 b propagates within theperipheral image injection optics 150 due to internal reflection on thereflective surfaces 152, 153 and 154 while it expands to the secondangle β, towards an imaging in-coupling element 35. The peripheral imageinjection optics 150 creates a peripheral modulator image 114 b of theSLM 20. In this configuration, a peripheral modulated light beam 110 bfrom each pixel of the image 114 b is collimated by the beam shapingreflective surface 154 and is injected by the imaging in-couplingelement 35.

In the embodiments shown in FIGS. 1 a to 1 f , the optical combinercomprises the foveal combiner 41 and a peripheral combiner including animaging exit pupil expansion device 36 configured to receive theperipheral modulated light beams 110 b and project the peripheral imagelight beams 112 b along the projection axis 170 within the peripheraleye-box 121 b. The collimated peripheral modulated light beams 110 b(the peripheral modulated light beams 110 b include beams from each SLMpixel, these pixel beams are collimated) with expanded second β areinjected into the imaging exit pupil expansion device 36 through theimaging in-coupling element 35. The imaging exit pupil expansion devicecan comprise an imaging waveguide 36.

The imaging waveguide 36 can comprise an imaging out-coupling element 37configured to allow the peripheral image light beams 112 b to exit theimaging waveguide 36 and be projected along the projection axis 170 bwithin the peripheral eye-box 121 b. The peripheral eye-box 121 b istypically larger than the foveal eye-box 121 a due to pupil replicationthat is performed by the imaging waveguide 36.

FIG. 1 d illustrates the near-eye image projection system 200, wherein asubset of peripheral modulated light beams 110 b (namely one peripheralmodulated light beam 110 b), is transmitted through the Fourier filter34, injected in the imaging waveguide 36 and peripheral image lightbeams 112 b are projected along the projection axis 170 b within theperipheral eye-box 121 b.

FIG. 1 e illustrates the near-eye image projection system 200, wherein asubset of (two) foveal modulated light beams 110 a is reflected on theimaging mirror 32 and the foveal combiner 41, and the foveal image lightbeams 112 a are projected along the projection axis 170 a within thefoveal eye-box 121 a. The imaging deflecting elements 60 a can reflectthe incident light beams 110 a in different angles such that wherein atleast some of the foveal modulator images elements 114 a are focused atdifferent locations in the plane 115 relative to other foveal modulatorimages 114 a.

FIG. 1 f illustrates the near-eye image projection system 200 of FIG. 1e , further showing a subset (namely one) of peripheral modulated lightbeams 110 b are injected in the peripheral combiner (imaging exit pupilexpansion device 36) and the corresponding peripheral image light beams112 b are projected along the projection axis 170 b within theperipheral eye-box 121 b.

In FIGS. 1 c, 1 e and 1 f , the pin-light source 10, SLM 20, prism 70and the illumination pupil expansion device 36 a are representedschematically by a box 200.

The imaging out-coupling element 37 can comprise a volume hologram,diffraction grating mirror arrays or stack of prism (semi-transparentinterfaces). The out-coupling element 37 and the waveguide 36 are usedas the peripheral combiner and, thus, need to be partly transparent inaugmented reality applications. They can be non-transparent for virtualreality applications and video pass-through augmented realityapplications. The foveal combiner 41 can comprise a wide range ofsemi-transparent optical devices, such as volume holograms, Fresneltypes of reflectors, or ellipsoid surface with semi-reflective innersurface.

The near-eye image projection system 200 allows for projecting thefoveal modulated light beams 110 a and the peripheral modulated lightbeams 110 b, via the optical combiner 40, along the projection axis 170a, 170 b to the eye-boxes 121 a and 121 b as foveal image light beams112 a and peripheral image light beams 112 b, respectively.

Other configuration of the illumination optics can be contemplated. Forexample, in FIG. 2 b , the illumination collimating element 50 anddeflecting element 61 comprises an hologram. In FIG. 2 e , the functionsof the collimating element 50, imaging deflecting element 60 a and ofthe illumination in-coupling element 35 a are performed by a singleholographic of diffractive element 35 a.

FIG. 4 a represents a foveated region of the field of view as seen fromthe foveal eye-box 121 a. The image comprises a narrow field of viewlight-field part 11 and a wider field of view peripheral image 12.

FIG. 4 b represents an actively foveated image as seen from theperipheral eye-box 121 a. The actively foveated image can be obtained inthe case the near-eye image projection system 200 comprises aneye-tracking and steering device and a movable imaging mirror 32. Thenarrow field of view light-field part 11 can be moved from a centralposition based on information about the viewer's eye gaze or accordingto the displayed content, with respect to the wide field of view image12.

The present disclosure further pertains to a wearable device comprisingthe image projection system 200.

FIG. 5 is a schematic representation of mixed reality glasses comprisingthe image projection system 200 on each temple, according to anembodiment. In the right side of the glasses, the pin-light source 10,SLM 20, prism 70, imaging mirror 32, Fourier filter 34, illuminationpupil expansion device 36 a and illumination out-coupling element arerepresented. The right temple is not shown. The foveal combinercomprises a lens 41 (glass lens). The imaging exit pupil expansiondevice 36 and the imaging out-coupling element 37 forming the peripheralcombiner are embedded in the lens 41. On the left side of the glasses,the image projection system 200 is integrated into the temple.

FIG. 6 is a top view of the mixed reality glasses of FIG. 5 , worn by auser. The image projection system 200 can be included only on one sideof the mixed reality glasses with the optical combiner 40 beingcomprised in at least one of the lenses 41 of the glasses (as describedabove). The image projection system 200 can be included in the hinges oranother portion of the temples.

REFERENCE NUMBERS AND SYMBOLS

-   10 pin-light source-   10 a active pin-light-   11 foveated region of the field of view-   12 peripheral region of the field of view-   13 peripheral pin-light subarray-   20 optical light modulator (SLM)-   30 first plane-   31 foveal pin-light image-   32 imaging mirror-   34 Fourier filter-   341 opening-   35 imaging in-coupling element-   35 a illumination in-coupling element-   36 imaging exit pupil expansion device, imaging waveguide-   36 a illumination pupil expansion device, illumination waveguide-   37 peripheral out-coupling element-   37 a illumination out-coupling element-   38 third plane-   39 peripheral pin-light image-   40 optical combiner-   41 foveal combiner, lens-   50 collimating optical element-   52 first beam shaping outer surface-   53 second beam shaping outer surface-   54 third beam shaping outer surface-   56 quarter-wave plate-   58 fourth beam shaping outer surface-   61 illumination deflecting element-   60 a imaging deflecting elements-   70 illumination and projection optical element, prism-   90 eye-   92 retina-   100 a foveal incident light beam-   100 b peripheral incident light beam-   110 a foveal modulated light beam-   110 b peripheral modulated light beam-   112 a foveal image light beams-   112 b peripheral image light beams-   114 a foveal modulator image-   114 b peripheral modulator image-   115 modulator image plane-   120 second pin-light images, viewpoints-   121 a foveal eye-box-   121 b peripheral eye-box-   124 second plane-   125 fourth plane-   130 pupil-   140 beam splitter-   150 image injection optics-   151 beam shaping transmissive surface-   152 reflective surface-   153 reflective surface-   154 beam shaping reflective surface-   170 a projection axis-   170 b central viewing axis-   171 first optical path-   172 second optical path-   173 third optical path-   174 fourth optical path-   190 real world-   200 image projection module

1. A near-eye image projection system, comprising: a pin-light sourcegenerating a plurality of incident light beams; a spatial lightmodulator (SLM) configured to modulate said plurality of incident lightbeams and generate a plurality of modulated light beams such as to formpin-light images at a first plane; illumination optics and imagingoptics configured to deliver the incident light beams from the pin-lightsource to the SLM; and the imaging optics being further configured todeliver sequentially the modulated light beams from the SLM along aprojection axis to an eye-box in a second plane substantially parallelto the first plane; wherein the illumination optics is in a third planeand the projection axis is in a fourth plane, the third and fourthplanes being substantially perpendicular to the first plane; theillumination optics defines a first optical path followed by theincident light beams in a direction from the first plane to the secondplane and a second optical path followed by the incident light beams ina direction from the third plane to the fourth plane; and the imagingoptics defines a third optical path followed by the modulated lightbeams in a direction from the second plane to the first plane and afourth optical path followed by the modulated light beams in a directionfrom the first plane to the second plane; wherein the imaging opticscomprises an optical combiner to project image light beams from themodulated light beams and to transmit natural light from the real worldtowards the eye-box; wherein the modulated light beams comprise fovealmodulated light beams forming foveal pin-light images at the first planeand peripheral modulated light beams forming peripheral pin-light imagesat the first plane; and wherein the optical combiner comprises a fovealcombiner configured to reflect the foveal modulated light beams andproject foveal image light beams towards a foveal eye-box.
 2. Theprojection system according to claim 1, wherein the illumination opticscomprises an illumination pupil expansion device configured to expandthe incident light beams from an entrance of the illumination pupilexpansion device to an exit pupil.
 3. The projection system according toclaim 2, wherein the illumination pupil expansion device comprises aillumination waveguide including an illumination in-coupling elementconfigured to input the incident light beams.
 4. The projection systemaccording to claim 3, wherein the illumination waveguide comprises anillumination deflecting element configured to redirect the incidentlight beams along the first optical path and an illuminationout-coupling element configured to output the incident light beams alongthe second optical path.
 5. The projection system according to claim 3,wherein the illumination waveguide further comprises collimating elementconfigured to collimate said plurality of incident light beams.
 6. Theprojection system according to claim 3, wherein the illuminationwaveguide comprises 1D or 2D fold gratings configured to interact withsaid plurality of incident light beams.
 7. The projection systemaccording to claim 1, wherein the SLM (20) is reflective. 8.-17.(canceled)
 18. The projection system according to claim 1, wherein theimaging optics comprises a Fourier filter in the first plane.
 19. Theprojection system according to claim 18, wherein the Fourier filtercomprises imaging deflecting elements in the first plane reflecting thefoveal modulated light beams to the foveal combiner.
 20. The projectionsystem according to claim 19, wherein the imaging optics comprises animaging mirror configured to reflect to the foveal combiner the fovealmodulated light beams reflected by the imaging deflecting elements. 21.The projection system according to claim 20, wherein the imaging mirroris movable such as to deflect from the projection axis the fovealmodulated light beams reflected by the imaging mirror.
 22. Theprojection system according to claim 21, comprising an eye-tracking andsteering device providing eye-tracking information; and wherein theimaging mirror is movable in accordance with eye-tracking information.23. The projection system according to claim 18, wherein the Fourierfilter is configured such that the peripheral modulated light beams canenter an injection optics, the injection optics being configured toexpand the peripheral modulated light beams from a first angle (α) to asecond angle (β) larger than the first angle (α).
 24. The projectionsystem according to claim 23, wherein the imaging optics comprises animaging exit pupil expansion device configured to receive the peripheralmodulated light beams and project peripheral image light beams along theprojection axis within the peripheral eye-box region.
 25. The projectionsystem according to claim 24, wherein the imaging exit pupil expansiondevice comprises an imaging waveguide, the imaging waveguide includingan imaging in-coupling element configured to input the peripheralmodulated light beams in the imaging waveguide, and an imagingout-coupling element configured to project the peripheral image lightbeams along the projection axis within the peripheral eye-box region.26. A wearable device comprising a projection system comprising apin-light source generating a plurality of incident light beams; a SLMconfigured to modulate said plurality of incident light beams andgenerate a plurality of modulated light beams such as to form pin-lightimages at a first plane; illumination optics and imaging opticsconfigured to deliver the incident light beams from the pin-light sourceto the SLM; and the imaging optics being further configured to deliversequentially the modulated light beams from the SLM along a projectionaxis to an eye-box in a second plane substantially parallel to the firstplane; wherein the illumination optics in in a third plane and theprojection axis is in a fourth plane, the third and fourth planes beingsubstantially perpendicular to the first plane; the illumination opticsdefines a first optical path followed by the incident light beams in adirection from the first plane to the second plane and a second opticalpath followed by the incident light beams in a direction from the thirdplane to the fourth plane; and the imaging optics defines a thirdoptical path followed by the modulated light beams in a direction fromthe second plane to the first plane and a fourth optical path followedby the modulated light beams in a direction from the first plane to thesecond plane; wherein the imaging optics comprises an optical combinerto project mage light beams from the modulated light beams and totransmit natural light from the real world towards the eye-box; whereinthe modulated light beams comprise foveal modulated light beams formingfoveal pin-light images at the first plane and peripheral modulatedlight beams forming peripheral pin-light images at the first plane; andwherein the optical combiner comprises a foveal combiner configured toreflect the foveal modulated light beams and project foveal image lightbeams towards a foveal eye-box.
 27. The wearable device according toclaim 26, comprising mixed reality glasses, wherein the optical combineris comprised in at least one of the lenses of the glasses, theillumination optics and the imaging optics are comprised in the hingesor another portion of the temples.